Patent Literature 1 discloses an exterior louver formed as a hollow extruded cement plate.
A panel formed as a hollow extruded cement plate, such as the exterior louver disclosed in Patent Literature 1, is too heavy to install easily. In addition, such a panel also requires curing. Thus, it takes a lot of time and trouble to manufacture such a panel.
Besides, the material itself of the hollow extruded cement plate tends to crack or peel easily. Therefore, part of an exterior louver formed as such a hollow extruded cement plate could drop off either during or after its installation.